Device for linking conveyor belts, method for making same and method for mounting same on a conveyor belt

ABSTRACT

One of the junction devices for a conveyor belt comprises three parts, namely an upper part ( 2 ), a lower part ( 3 ) and an intermediate part ( 4 ). Inserts ( 6′ ) and ( 7′ ) are used to assemble parts ( 2 ) and ( 3 ) using screws ( 5 ). Inserts ( 6 ) and ( 7 ) are used to assemble the junction device on the ends of a conveyor belt.

[0001] This invention relates to the field of non-disconnectablejunction devices intended to join together the ends of conveyor belts.For simplification purposes, the term “conveyor belt” in thisdescription will be used to refer to conveyor belts and powertransmission belts.

[0002] In the past, junction devices have been used with a generalH-shaped section that can be fixed on the ends of a conveyor belt. Thesejunction devices comprise two pairs of attachment flanges correspondingto the flanges of the H-shaped section and an intermediate central partthat corresponds to the web of the H-section. One of the ends of theconveyor belt is inserted between one of the pairs of flanges, and theother end is inserted between the other pair. The flanges are attachedto the ends of the conveyor belt by means of rivets, nails, crampons,screw-nut systems or by cold gluing or flat vulcanisation of the flangesin contact with the flat outside surfaces of the conveyor belt engagedbetween the flanges. These junction devices are made of a flat elasticflexible material such as vulcanised rubber, or a synthetic materialsuch as polyurethane, and they contain a built-in reinforcement.However, the proposed reinforcements were made of an ordinary fabric,and were not capable of sufficient elongation to pass over the conveyorbelt drive or return rollers without causing damage to the junctiondevice installed at the ends of the conveyor belt.

[0003] The applicant for this patent has deposited a previous patentdivulging the use of fabrics or knits. For fabrics, he described the useof fabrics comprising a deliberately loosely woven weft so that thisweft in the longitudinal direction would deform until the weft threadsbecome tightened and transmit tension, in order to absorb the differentpath distances that occur in the junction device when passing over thedrive or return rollers around which the conveyor belt on which thejunction device is installed passes without any damage being caused, theloose threads thus tightened would be capable of transmitting a tensionforce for which they are designed, then being brought back together bythe constituent material. The applicant for this patent had alsodescribed the use of platelets or washers in the flanges of the junctiondevices designed to fix these devices to the ends of the conveyor belt,these platelets or washers comprising a hole through which nails,rivets, crampons, screws or any other devices with a rod designed topass through a flange, the conveyor belt and then the other flange couldbe inserted, and being fixed on the other side of the other flange. In aversion comprising cables, the washers were anchored to thereinforcement composed of cables, through loops formed by these cablesand surrounding the perforated washers. In the case of a fabric orknitted reinforcement, holes were formed in the flanges and consequentlyin the reinforcement.

[0004] Despite the essential improvements included in the solutionsproposed in the past by the applicant for this patent application, itwas found in practice that there were still limitations on the use ofthe resulting junction devices, namely:

[0005] fabrics with weft butt joints ??? were not sufficiently flexiblein the direction of motion of the conveyor belt when passing over somedrive or return rollers encountered in practice,

[0006] the construction of a channel-shaped conveyor belt was toodifficult due to the excessive stiffness of the junction devicepreventing it from satisfactorily following the conveyor belt when theedges of the belt were lifted up for bulk transport purposes,

[0007] in some cases, attachment of the flanges using single perforatedreinforcing washers with conventional attachment means caused tearing ofthe reinforcements at the location of the holes formed in thereinforcements, and the resistance of the reinforcements was reduced dueto the large number of small lesions caused by these holes,

[0008] junction devices made by moulding or by injection required adifferent mould for each thickness of conveyor belt used in practice,for their production, and consequently they had to be manufactured invery small series which increased the cost price, and the manufacturing,storage and distribution price.

[0009] The purpose of this invention is to propose solutions to theproblems described above.

[0010] The applicant discovered that to solve the problem of thenecessary extendibility of the flanges of junction devices provided withfabric reinforcements, it was useful if the texture of the fabrics wasloose or if it was strongly curved ??? in weft and in warp. Theapplicant also discovered that with these fabrics with a loose warp andweft, it was possible to use fabrics in one or several layers in twodifferent arrangements.

[0011] According to a first arrangement, the reinforcing fabrics arearranged so that the direction of the warp or the weft is parallel tothe longitudinal direction of the junction devices, in other words byconvention along the direction of motion of the conveyor belt that mustbe fixed to it, independently of the effective dimensions of thejunction devices. Similarly in this description, by convention, thetransverse direction of the junction device will be the directionperpendicular to the longitudinal direction defined above.

[0012] According to a second arrangement, the reinforcing fabrics inwhich the warp and the weft are loosely woven, are arranged such thatthe warp or the weft are equally loose and form an angle from thelongitudinal direction of the junction device, regardless of whether thefabric is arranged in a single layer or in several layers. The optimumangle is found to be approximately 45°.

[0013] All that has been said above about loosely woven fabrics that areloose in warp and in weft, is also applicable for knits, that can beknitted loosely in warp, while adding a weft that can be insertedloosely.

[0014] Using the solutions mentioned above, the applicant obtainedreinforcements sufficiently flexible to accommodate all elongationnecessary for the conveyor belts to pass over all rollers that have beenencountered in practice.

[0015] However, the problems caused by attachment of the flanges ontothe ends of conveyor belts, and particularly the problem caused bylesions in the reinforcements, have not been solved despite theimprovements to the structure of the reinforcement described above.

[0016] Therefore, the applicant has designed and developed improvedwashers that are put into place so as not to cause any damage (or in anycase only slight damage) to the woven or knitted reinforcement. Thesewashers comprise a recess that will contain the head of the attachmentmeans with a stem, this recess being extended as a tubular part, atleast in some of the washers. The washers also comprise at least one pinoriented in the same direction as the recess, in other words towards thereinforcement, this pin being located at the periphery of the washer andpreventing rotation of the washer. The reinforcement, composed of one orseveral layers of fabric or knit as described above, is arranged aroundthe tubular part extending the recess perpendicular to the general planeof the washer such that the edges of the reinforcement surrounding thetubular part are raised along the tubular part also forming a rightangle, or approximately a right angle, with the plane of thereinforcement. These raised edges of the reinforcement bond to thetubular part. With this conformation of the washer and its arrangementin the reinforcement, the reinforcement is not perforated consequentlycausing wires to be cut in the fabric or the knit, and instead thethreads are simply separated. Obviously, it is possible that a threadcan break but the lesion thus caused is much less serious than thelesion created by conventional holes cut in flanges by drilling or bypunching. Furthermore, the diameter of the washer can be reduced due tothe fact that the washer not only bonds flat to the reinforcementthrough its head, but it also bonds in the perpendicular directionthrough the outside surfaces of the tubular part to the raised edges ofthe reinforcement. Thus, the anchorage of the recess in the flange ofthe junction device is particularly good.

[0017] Furthermore, due to the fact that the head of the washer head issmall, if necessary it may pivot by a few degrees from the perpendicularto the general plane of the flange considered due to the articulationcaused by the fact that the angle formed between the plane of themajority of the reinforcement and its raised edges bonding to thetubular part of the washer, this capability being useful in combinationwith the attachment means described below. These washers thus shaped andplaced are arranged in the flanges of the lower part.

[0018] In the upper part, the washers consist only of a perforatedrecess without a tubular part, and in the lower part the washers consistof a recess extended by a tubular part as described above. The tubularpart of these washers is threaded on the inside. This arrangementenables the use of screws as an attachment means. A screw, preferably aself-tapping screw, inserted into the washers without a tubular part isscrewed into the end of the conveyor belt after being inserted into thespace between the two flanges of the same pair, until it stops incontact with the intermediate part of the junction device; the screwthen enters the threaded hole in the tubular part of the washer in theother flange, the relative mobility of the tubular part with respect tothe perpendicular to the general plane of the washer enabling mutualself-centering of the screw in the tubular part. By screwing into thetapped thread, the screw exerts a high tension on the washer through thetubular part of the washer, this tension causing efficient clamping ofthe two flanges in contact with the plane outside surfaces of the end ofthe conveyor belt. This tension is transmitted to the lower flange, boththrough the head of the washer and the outside surface of the tubularpart to which the reinforcement is bonded, the surfaces of thereinforcement and the tubular part working in shear.

[0019] In practice, the washers and consequently the screws, arearranged to be staggered on the surface of the flanges to optimisedistribution of the tightening points.

[0020] Additional improvements are explained later as part of thedescription of a preferred embodiment with reference to the figures inthe drawing illustrating this description.

[0021] However, due to the excellence of these flange attachment meansto the ends of the conveyor belt, the applicant has been able to solvethe other problem that occurred initially, namely the problem of thelarge number of moulds and moulded products necessary for the variousthicknesses of conveyor belts. The solution found consists of makingjunction devices in three separate parts; one part forming the left andright top flanges in a single piece, apart forming the left and rightbottom flanges in a single piece, and an intermediate part correspondingto the central web of the H-section.

[0022] The top part comprises two or several washers of the typeprovided with a tubular part, smooth on the inside, built into the toppart on a median line forming an imaginary separation between the leftflange and the right flange, the tubular parts of the washers facingdownwards.

[0023] The bottom part is provided with two or several washers of thetype comprising a threaded tubular part built into the bottom part on amedian line forming an imaginary line separating the left flange fromthe right flange, the tubular threaded parts facing upwards.

[0024] It should be clear that the concepts of top and bottom are onlyuseful for the purposes of the description and that in practice they canbe inverted.

[0025] The intermediate part is parallelepiped shaped, and it can beproduced, stored and distributed in several different heights comprisingbuilt in bushings that pass through them in the direction of the height,and that have the same spacing as the built-in washers in the middle ofthe top and bottom parts, so that the built-in washers can be alignedwith the top and bottom parts when the top and bottom parts are arrangedon each side of the intermediate part. The diameters of the cylindricalassemblies composed of the tubular parts of the washers comprisingraised parts of the reinforcement bonding to their outside surface andlayers of rubber or synthetic material between which the reinforcementlayers are sandwiched, are such that these cylindrical assemblies can beinserted in the corresponding bushings in the intermediate part. Thus,it is possible to screw in screws with a head that fits in the recessesof the inserts with a smoothed tubular part, the threaded stems of thescrews passing through the bushings without screwing into them since theinside diameter of the bushing is greater than the outside diameter ofthe screw by at least twice the thickness of the reinforcementsurrounding the tubular part of the washer. The screws are then screwedinto the tapped thread of the threaded tubular parts of the built-inwashers as described above, in the middle area of the lower parts.

[0026] Additional improvements will be described later in relation to apreferred embodiment illustrated by the figures.

[0027] Tests carried out showed not only the excellent quality of thisassembly according to the invention, but manufacturing is also very muchsimplified compared with a junction device made from a single piece bymoulding or by injection. The manufacture of the reinforcements andtheir arrangement in the moulds is very much simplified by making anupper part with a left upper flange and a right upper flange separatelyand connected by a median part, a lower part comprising a lift lowerflange and a right lower flange connected by a median part, and anintermediate part provided by bushings that can be made in severaldifferent lengths.

[0028] One preferred embodiment of the invention will now be describedin detail with reference to the drawings in which:

[0029]FIG. 1 is a plan view of a junction device according to thisinvention, seen from above,

[0030]FIG. 2 is an exploded view of a longitudinal section along lineA-A in FIG. 1 of a junction device according to this invention, showingthe various component elements,

[0031]FIG. 3 is a longitudinal section along line A-A in FIG. 1, showingthe junction device according to this invention in FIG. 2, its threeelements being assembled according to the invention,

[0032]FIG. 4 is an enlarged fragmentary sectional view of the assemblymethod shown in FIG. 3,

[0033]FIG. 5 is a sectional view along line A-A in FIG. 1 of thejunction device according to this invention shown in FIG. 3, installedon the two ends of a conveyor belt,

[0034]FIGS. 6, 7 and 8 show the successive phases in setting up athreaded insert in the lower part of a junction device according to theinvention.

[0035]FIG. 1 is a plan view seen from above showing a junction deviceaccording to this invention, and shows a top plate 2 of a junctiondevice 1. Note also the heads of screws 5 that form the preferred meansof assembly of junction devices according to the invention used in thepreferred embodiment described herein. The exploded views 11 a and 11 bshow two types of woven reinforcement according to the invention; intype 11 a the fabric is arranged such that its weft threads, or its warpthreads, are oriented at least approximately along the longitudinaldirection of the junction device. Remember that by convention, for thepurposes of this description, the longitudinal direction of the junctiondevice is the longitudinal direction of the conveyor belt BT in FIG. 1,the junction device being mounted on the ends of the conveyor belt BTthat it joins. According to the same convention, the transversedirection of the junction device is the direction perpendicular to thelongitudinal direction. This convention is applied regardless of theeffective dimensions of the junction device in the two directions. Thejunction device in FIG. 1 is composed of three elements, an elementforming an upper plate 2, an intermediate plate located under the medianpart of the plate that is not visible in FIG. 1 other than by the twodashed lines located on each side of the two median screws 5, and anelement forming a lower plate 3, not visible in FIG. 1, located underthe intermediate element and under the element forming an upper plate 2.

[0036] The exploded section in FIG. 2 shows a series of assembly screws5, the top plate 2, and inserts 6 and 6′ incorporated into the top plate2; the intermediate element 4 comprises an incorporated through bushing8 arranged vertically, the lower plate 3 comprising threaded inserts 7and 7′. The inserts 6 are usually in the form of drilled washerscomprising a recess that will hold the heads of the screws 5 that willpass through the holes in the drilled washers. Other details aredescribed later. The central insert 6′ is generally arranged like theinserts 6 but it comprises a central tubular part for which the innercylindrical surface D2 is designed to allow the corresponding screw 5 topass through it with a very small clearance, therefore this screw doesnot screw into the insert 6′. The central tubular part of the insert 6′projects beyond the lower surface (right on FIG. 2) of the upper plate2.

[0037] The inserts 7 each comprise a central tubular part of which theinner cylindrical surface is threaded and is capable of holding a screw5 screwed into the tapped thread, the said central tubular partsprojecting beyond the upper surface (left in FIG. 2) of the lower plateof the junction device. Details showing an important improvement aredescribed later in relation to FIG. 8. The median inserts 7′ of thelower plate are like the inserts 7.

[0038] The sectional view in FIG. 3 helps to understand the assembly ofthe three elements of the junction device according to the invention inthe form of a preferred embodiment described with relation to thedrawings. It shows screw 5 passing through the tubular part of thecentral insert 6′, its head being inserted in the recess and its stembeing provided with a male thread passing through bushing 8 of theintermediate element without screwing into it. The lower part of thisscrew 5 is screwed into the thread in insert 7′.

[0039] It will be seen that the junction device assembled in this way isready to be fitted onto the ends of a conveyor belt using the screwsshown in waiting above the top plate.

[0040]FIG. 4 shows a magnified fragmentary view of the screw assembly inFIG. 3. It shows the screw 5, inserts 6′ and 7′, the tubular part of theinsert 7′, the outer surface of the insert being bonded to the parts ofthe reinforcement separated around the tubular part during placement ofthe insert in the reinforcement during the manufacturing of the junctiondevice, as described later.

[0041] It will be seen that the outside diameter D2 of the part of thetop plate 2 surrounding the tubular part of the insert 6′ is veryslightly smaller than the diameter Dl of the bushing 8 of the insertelement 4, so that it can be inserted into the said bushing 8.Similarly, the diameter D3 of the part of the lower plate surroundingthe threaded tubular part of the insert 7′ is also very slightly lessthan the inside diameter Dl of the bushing 8.

[0042]FIG. 5, showing the same section as the previous figures, showsthe junction device according to the preferred embodiment fitted on theends 20, 20′ of a conveyor belt. The screws 5 are engaged in the insert6 and they pass through the thickness of the conveyor belt when they arescrewed in, without a pilot hole since they are self-tapping. Since therecesses in the inserts 6 are not prolonged by tubular parts, and sincethe diameter of the holes in the washers of the inserts 6 isdeliberately greater than the diameter of the threads of the screws 5,the screws 5 can easily oscillate if necessary, which may be the case ifthey are not perfectly centred in the threads of the inserts 7 afterpassing through the conveyor belt.

[0043] Important details in FIGS. 7 and 8 are that in the most advancedform of the preferred embodiment of the junction device according to theinvention, the threads of the inserts 7 and 7′ are coated with a coat ofthe material making up the junction device obtained duringvulcanisation, or when the junction device is moulded by injectionaccording to the process described later. Raised parts of thereinforcement can be seen, in this case composed of two layers of fabricor knit, sandwiched between the layers of vulcanised rubber, orsynthetic material such as polyurethane. These raised parts bond to theouter surface of the threaded cylindrical part of insert 7′.

[0044] The advantage of these raised parts and the coating 15 on thethread 16 on inserts 7 and 7′ will be described later.

[0045] We will now explain FIGS. 6 and 7 which will help to understandthe process by which the insert 7′ shown in the finished state in FIG. 8is incorporated.

[0046]FIG. 6 shows a layer of vulcanizable or thermoformable material 21shown in black, through which a nail 14 passes. This nail 14advantageously forms part of a vulcanisation half-mould (if the materialfrom which the basic junction device is made is a vulcanizable rubber)or an injection mould when the basic material used is a syntheticmaterial, for example a polyurethane. An insert 7′ is inserted above thelayer shown in black. Note that the stem diameter is less than thediameter of the tips of the tapping threads 16. This is donedeliberately to leave space so that later, during the vulcanisation orinjection step, the material can flow between the nail 14 and thetapping, consequently forming the coating 15 that can be seen in FIG. 8.The reinforcing layers are not yet threaded on the nail 14.

[0047]FIG. 7 shows the reinforcing layers threaded on the nail 14 andlaid out in contact with insert 7′, the pins 18 of the insert beingforced into the reinforcing layers and the layers of material betweenwhich they are sandwiched. Note that at this stage, in other wordsbefore the mould is closed and before vulcanisation, a space 22 shown inwhite separates the lower reinforcing layer and the upper reinforcinglayer 21 shown in black.

[0048] It will be understood that during vulcanisation, under the effectof pressure, the lower layer 21 of material is firstly forced intocontact with the lower reinforcing layer to which it bonds, and secondlyflows between the nail 14 and the thread of the insert 7′, thus formingthe coating 15 of the thread visible in FIG. 8.

[0049] Pins 18 forced into the two reinforcing layers sandwiched betweenthe rubber layers (or the layers of synthetic material) can also beseen. These pins 18, of which there may be one or several (for example4), are provided to prevent the threaded insert 7′ from rotating whenthe screw is screwed into the tapping 16, particularly since in the mostadvanced version of the preferred embodiment described herein, the screwexerts a large torque as it is screwed into the tapped thread.

[0050] Furthermore, pins 18 are advantageously provided on inserts 6, 6′and 7, and the same problem arises to prevent the inserts from rotatingwhile the screws 5 are being screwed in, however the pins are lessimportant in inserts 6 and 6′ since the screw only exerts a torque byfriction of the head in the recess of the inserts 6 and 6′ at the end ofscrewing. However, it is wise to provide at least one pin 18, or severalpins (for example 4) on all types of inserts.

[0051] If the constituent material used for the junction deviceaccording to the invention is a synthetic material such as polyurethanerather than vulcanizable rubber, a similar process is done usinginjection. This implies a few variants to the process described below.Firstly, the manufacture of the sandwiched reinforcement between thelayers of synthetic material is not as easy as it is in the case ofvulcanizable rubber. For a synthetic material such as polyurethane, animpregnation of the reinforcement, fabric or knit may be necessary usingan impregnation polyurethane; it would also be possible to use a roll ofpolyurethane sheets on the reinforcing layer(s). Furthermore, for theouter layer 21, this layer does not exist in advance as in the case ofvulcanised rubber, but it is created by injection in the mould in whichthe sandwich of reinforcing layers threaded on the nails 14 and on theinserts 16 is located. Thus, by proceeding in this way to take accountof injection needs, the end result for a synthetic material is the same,as shown in FIG. 8 with vulcanizable rubber.

[0052] The raised parts 17 of the reinforcement shown in FIGS. 7 and 8that are bonded to the outside surface of the inserts 7′ make it evenmore sensitive to tearing due to the fact that they work in shear andnot in separation of the flat bonding parts.

[0053] Another advantage of the method of laying out the inserts 7 or 7′that can be seen in the finished state in FIG. 8 is due to the fact thatthe tubular parts of the washers can oscillate slightly around theirnormal position, in other words perpendicular to the general plane ofthe flange. This is possible because:

[0054] The tubular part of the inserts 7 is fixed to the raised parts ofthe reinforcement arranged in the top part of the lower flange betweenthe thin layers from which the material is made.

[0055] The diameter of the washer part of the inserts 7 or 7′ is smallerand it bears on the thick layer 21 of the elastic constituent materialwithout any reinforcement between this layer 21 and the washer part ofthe insert 7 or 7′.

[0056] This possibility of oscillation around the perpendicular providesadvantages in three cases:

[0057] When the junction device is being fixed on the ends of theconveyor belt, firstly the screw can oscillate as described above withrespect to the washer part of the inserts 6, but also the tapped tubularpart of the inserts 7 can also oscillate causing self-centering of thescrew 5 and the threaded tubular part of the inserts 7 can be tappedwithout difficulty.

[0058] Therefore during use, when starting and stopping the conveyorbelt, the differences in acceleration (positive or negative) between thetop part of the conveyor belt that is loaded and therefore has a highinertia, and the lower part driven or braked by the drive device areeasily absorbed.

[0059]FIG. 8 shows dashed lines showing the positions of the tubularparts of the inserts 7 during acceleration or braking of the conveyorbelt. Therefore this configuration acts as a shock absorber.

[0060] Thus the coating 15 that could be considered as a disadvantagedue to the vulcanisation or moulding process, has an unexpectedadvantage. The screw 5 that engages into the coating to screw into thetapped thread is strongly locked so that it resists loosening that couldotherwise be caused for example by vibrations.

[0061] One variant of the invention allows for the outside diameter ofthe male thread to be slightly greater than the inside diameter of thebottom of the tapped thread. Screws made of a metal useable forself-tapping can be used so that the screw can engage more deeply intothe tapped thread, thus giving a very long lasting bond between thescrew 5 and the insert 7′.

[0062] The applicant has obtained even better results by using this typeof screw in which not only the outside diameter of the thread exceedsthe diameter of the tapped thread, but furthermore the pitch is not thesame as the pitch of the tapped thread. A screw thus shaped will more orless destroy the existing tapped thread, while creating a new largerdiameter tapped thread with a different pitch. The presence of debrisfrom the initial tapping in addition to the coating material 15 makesthe screws 5 thus screwed in almost unscrewable under the worst possibleusage conditions. This has been confirmed by tests.

[0063] Therefore, it is easy to understand the advantage of the pins 18present on the inserts, since they are often subject to high torques andtend to rotate while the screws 5 are being screwed into the threads ofthe inserts due to the conformations of the screws 5 and the tappedthread as described above.

[0064] Obviously, the preferred embodiment of the invention that wasjust described above does not exclude less sophisticated and lessambitious embodiments, but use the characteristics claimed in one ormore of the claims given below based on the description.

[0065] The above description of the incorporation of inserts shows thatseparate moulding of two plates and an intermediate element is muchsimpler than moulding an entire junction device that involvescomplicated operations for the placement of reinforcing layers, theinsertion of cores between the flanges allowing the nails to passthrough, and complex mould removal operations. On the contrary, theprocess proposed in the invention enables a “waffle mould” type mouldingthat is very efficient and the proposed assembly mode adds thepossibility of producing, storing and installing a variety ofthicknesses of junction devices with a minimum investment in moulds andstocks.

[0066] Finally, in the preferred embodiments, it will have been seenthat the top plate flanges comprise a relatively thick layer of materialused on the outside and that the reinforcement is laid outasymmetrically within the thickness of the flanges, the layers ofmaterials surrounding the reinforcement layers being thin. Thisconformation is not indifferent since it minimizes the thickness of theflanges of the junction devices, which is desirable for operation of theconveyor belt, and also allows the reinforcement according to theinvention to be more flexible as it passes over the drive or returnrollers while maintaining the excellent tension resistance qualities dueto the fact that the proposed assembly system does not cause any lesionsin the reinforcement of the junction devices or in the reinforcement ofthe conveyor belt.

1. Non-disconnectable junction device designed to connect the two endsof a conveyor belt in the general shape of an H-section comprising aflat upper part, a flat lower part and a median parallelepiped-shapedintermediate part placed between the flat upper part and the flat lowerpart made of a flexible elastic material provided with reinforcement,characterized in that the said reinforcement is composed of one orseveral layers of a textile that is flexible up to a defined limit inthe presence of forces exerted in a first direction and in the presenceof forces exerted in a direction at least approximately perpendicular tothe said first direction.
 2. Junction device according to claim 1,characterized in that the reinforcing layer(s) is (are) composed of aloosely woven fabric, loose in warp and in weft.
 3. Junction deviceaccording to claim 1, characterized in that the reinforcing layer(s) is(are) composed of a knit with a loose knitting in warp and comprising aninserted weft arranged loosely in the knit.
 4. Junction device accordingto claim 2 or 3, characterized in that the reinforcing layer(s) is (are)laid out such that in the case of the fabric, the warp threads or theweft threads of the fabric are arranged in the longitudinal direction ofthe junction device, the weft threads or the warp threads being arrangedin the transverse direction, or in the case of the knit, the warp of theknit or the weft inserted in the knit, are arranged in the longitudinaldirection of the junction device, the inserted weft in the knit or thewarp of the knit being arranged in the transverse direction of thejunction device.
 5. Junction device according to claim 2 or 3,characterized in that the reinforcing layer(s) is (are) laid out suchthat in the case of the fabric, the warp threads or the weft threads ofthe fabric are arranged to form an angle with the transverse directionof the junction device, or in the case of the knit, the warp of theknit, or the weft of the knit is arranged to form an angle with thetransverse direction of the junction device.
 6. Junction deviceaccording to claim 5, characterized in that the angle formed isapproximately 45°.
 7. Junction device according to one of the previousclaims, characterized in that it comprises inserts (6, 7) generally inthe form of washers incorporated in the flanges of the upper part (2)and in the flanges of the lower part (3), the central part of the saidinserts (6) being provided with recesses facing downwards and the saidrecesses comprising a hole in their centre, the said inserts (7)consisting of a washer comprising a recess at its centre prolonged inthe central area by a threaded tubular part facing upwards.
 8. Junctiondevice according to clam 7, characterized in that the holes of therecesses of the inserts (6) have a diameter greater than the diameter ofthe threads of screws
 5. 9. Junction device according to claim 7,characterized in that the inserts (6) and (7) each have at least one pin(18) located at the periphery of the washers of inserts (6 and 7)oriented in the same direction as the recesses of the inserts. 10.Junction device according to claim 8, characterized in that the pins(18) are fitted into the reinforcement of the flange in which thecorresponding inserts are located.
 11. Junction device according to anyone of the previous claims, composed of three distinct parts assembledby screwing, namely: a flat upper part (2) comprising inserts (6′)similar to the inserts (7) of the flanges in the lower part (3), in itsmedian area between the left and right flanges, with the difference thattheir tubular part facing downwards is smooth on the inside and is notthreaded, a flat lower part (3) comprising inserts (7′) in its medianarea identical to the inserts (7) in the flanges in the flat lower part(3), an intermediate (4) parallelepiped shaped element placed betweenthe median areas of the upper part (2) and the lower part (3),comprising built-in bushings arranged vertically in the intermediateelement such that they can be placed to be aligned with the tubularparts of the inserts (6′) and (7′), the inside diameter (D1) of thebushings (8) being slightly greater than the diameters (D2) of the partof the upper plate (2) surrounding the tubular part of the inserts (6′),and the diameter (D3) of the part of the lower plate 3 surrounding thetubular part of the inserts (7′), these three parts being assembled bymeans of screws (5) passing through inserts (6′) passing inside thebushings (8) and screwed into the threads of the inserts (7′). 12.Junction device according to claim 10, characterized in that the flatupper parts (2) and the flat lower parts (3) are each composed of alayer (21) of rubber or synthetic material, under which, or on which,inserts (6, 6′, 7, 7′) are placed such that their recesses or, whenapplicable, their tubular parts are facing downwards for the upperplates (2), and upwards for the lower plates (3), one or several layersof fabric or reinforcing knit being placed under the inserts for the topplates, and on the inserts for the bottom plates, such that the layersof fabric or knit are coated on each side with a thin layer ofconstitutive material, identical or compatible for vulcanising ormoulding with the layer (21) that is relatively thick compared with thelayers of constitutive material separating and coating the layers offabric or knit making up the reinforcement, the said layers ofconstitutive material forming part of the layer(s) of fabric or knit,and with the thick layer (21) of constitutive material.
 13. Junctiondevice according to claim 11, characterized in that the layers of fabricor knit, and the thin layers of constitutive material separating themand coating them, form a single unit with them, and are raised incontact with the outside surface of the tubular part of the inserts thathave a tubular part, in other words inserts 7, 7′ and 6′ with which theybond, leaving the end of the tubular part of the inserts 7, 7′ and 6′ toproject, regardless of whether or not they are threaded.
 14. Junctiondevice according to claim 12, characterized in that the tapped threadsin the tubular parts of the inserts 7, 7′ and 6′ are coated with a layerof constitutive material that fills in the hollows in the threads. 15.Junction device according to one of the previous claims, characterizedin that the screws (5) used for the assembly of junction devicesaccording to the invention, and for their attachment to the ends of aconveyor belt, are self-tapping screws.
 16. Junction device according toclaim 14, characterized in that the diameter of the male thread on thescrews (5) is greater than the diameter of the tapped female threads inthe tubular parts of the inserts 7, 7′ and 6′.
 17. Junction deviceaccording to claim 15, characterized in that the pitch of the screws (5)is not the same as the pitch of the tapped threads in the tubular partsof the inserts 7, 7′ and 6′.
 18. Manufacturing process for a junctiondevice according to any one of claims 10 to 16, characterized in thatthe upper and lower plates made of vulcanizable rubber are manufacturedusing two half-moulds, one of which is provided with nails 14 startingfrom the bottom of the mould and in that the following operations arecarried out in sequence: a) a relatively thick layer (21) ofvulcanizable rubber is threaded on the nails until it reaches the bottomof the mould; b) the inserts 6, 6′, 7 and 7′ are threaded on the nails,the recesses and tubular parts being arranged in the opposite directionto the relatively thick layer (21) of vulcanizable rubber; c) thelayer(s) of reinforcement fabric or knit are threaded on the nails,after being coated with a thin layer of vulcanizable rubber such that inthe case of a single layer of fabric or reinforcement knit, it will becoated on both sides by a thin layer of vulcanizable rubber inseparablefrom it and facilitating its manipulation, and that in the case in whichthere are two or more layers of fabric or knit, the layers are separatedby one or more thin layers of vulcanizable rubber incorporated onto it,the outer faces of the lower and upper layers of the sandwich thusformed being coated with a thin layer of rubber incorporated with it,the reinforcement thus created forming parts raised along the outsidesurface of the tubular parts of the inserts (7, 7′, 6′) when there areany inserts; d) the upper half-mould is put into place on the lowerhalf-mould, pressure is applied to close the mould and so thatvulcanisation can be done in a known manner; e) under the effect ofpressure, the thick layer (21) of vulcanizable rubber comes into contactwith the reinforcement by closing the inserts and creeps in the mould,in particular filling up the space between the threads of the inserts(7, 7′ and 6′) and the nails (14) on which these inserts are threaded;f) the mould is removed by separating the parts from the nails (14). 19.Junction device according to claim 17, characterized in that the layersof fabric or knit for reinforcement are applied successively, the layersfirstly being coated with a thin layer of vulcanizable rubber. 20.Process for manufacturing a junction device according to any one ofclaims 1 to 16, and partially according to claim 17 or claim 18,characterized in that the material used is a polyurethane or anothermaterial that can be moulded by injection, the manufacturing processbeing similar to the process according to claims 18 and 19 above, withthe difference that the thick layer (21) of polyurethane or othermaterial that can be moulded by injection does not exist in advance butis formed in contact with the reinforcement threaded on the nails (14)during an injection operation that also causes coating of thereinforcing layer(s), the formation of the coating (15) between thenails (14) and the tapped threads of tapped inserts, the layer(s) ofreinforcement possibly being impregnated with impregnating polyurethaneor any other material, before they are placed individually or in aprefabricated sandwich on the nails (14).
 21. Process for manufacturingthe junction device according to one of claims 10 to 16, characterizedin that conventional vulcanisation or injection moulds are used for themanufacture of intermediate elements (4) in which bushings (8) arefixed, these elements being made with different heights using differentmoulds or transformable moulds.
 22. Process for manufacturing a junctiondevice according to any one of claims 10 to 16, characterized in thatthe top part (2) and the bottom part (3) are assembled by screws (5)passing in turn through the inserts (6′), bushings (8) and screwing intothe tapped threads in the inserts (7′).